The proposed research continues our collaborative genetic and biochemical attack on the identification, organization and function of mitochondrial genes of bakers' yeast, Saccharomyces cerevisiae. We are concentrating at this time on the varl gene and flanking sequences. The region under study determines the size of the varl protein, a component of mitochondrial, whose size varies in different yeast strains. However, nucleotide sequence analysis indicate that the varl contains little, if any, of the coding sequences for the varl polypeptide, indicating that the structure of expression of this gene is novel. During this project period we will: (1) Complete and analyze the nucleotide sequence of the allele which determines the size of the largest varl polypeptide; (2) determine the sequence alteration in mutants of the varl region which affect mitochondrial protein synthesis; (3) sequence the 16s variable RNA from fast and slow strains. This RNA species is at least in part complementary to the varl region; (4) localize the varl structural gene; (5) further purify and characterize the varl polypeptide from fast and slow strains. We will concentrate particularly on obtaining amino acid sequence data from the amino terminal end; (6) continue to study nuclear suppressors of varl mutants; and (7) better localize the varl alleles and mutant sites in PZ200L, PZ200R and PZ206, and isolate petite strains containing the above mutant sites for use in DNA sequencing.